Air blast circuit breakers



Jan. 24, 1961 H. FORWALD 2,969,446

AIR BLAST CIRCUIT BREAKERS Filed Jan. 28, 1958 IN VEN TOR. f/AH KON FOR W/IL D Warn 6 Y titted 1 AIR BLAST CIRCUIT BREAKERS Haakon Forwald, Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Jan. 28, 1958, Ser. No. 711,610

Claims priority, application Sweden Feb. 1, 1957 Claims. (Cl. 200-148) The present invention relates to an air blast circuit breaker, especially for indoor switch gears, for low and medium voltages with one breaking gap in an earthed compressed air tank with a pair of leading through insulators arranged opposite each other, each of which carries the contacts of the breaking gap.

In circuit breakers of this kind hitherto a movable contact as well as a blast valve were arranged in the same leading through insulator. In one execution form a mechanism unit with a movable contact and a blast valve together with their operating members were arranged inside of the leading through insulator at its inner end. In another form the movable contact was designed as a tube contact entirely passing through the leading through insulator and connected at the outer part of the insulator with the valve members of the blast valve and with an operating member common to the contact and to the valve. The blast valve as well as the operating members were then arranged in an operating housing quite outside the outer end of the leading through insulator. The said circuit breakers, in which the blast valve and the movable contact are carried by the same leading through insulator, are however combined with various inconveniences. It is thus difiicult to carry out the circuit breaker in such a way that the movable contact and the blast valve can be operated individually. The mass of the movable parts has also become so large that the insulator is exposed to unduly large stresses when the mass is retarded. This has especially been the case at breakers with a hollow contact that entirely passes through its leading through insulator and is operated by an operating mechanism located outside the outer part of the insulator.

The above mentioned drawbacks are avoided by the invention in that the one leading through insulator of the circuit breaker carries a movable contact, which is joined with an operating piston movable in a cylinder, and in that the other leading through insulator of the circuit breaker carries a stationary nozzle contact and a blast valve and is provided with an outlet channel for the blast air. The said operating piston for the movable contact is so arranged that it is actuated in opening direction by the pressure in the container. The blast valve is suitably located in a mechanism housing arranged at the outer part of the leading through insulator and connected with an operating piston in an operating cylinder joined with the valve housing. By arranging the movable parts of the circuit breaker in the said way, their masses can be made small and the stresses in the insulators at retarding the masses can be small. The movable contact and the blast valve can be operated individually so that the valve can be opened before the breaking gap is opened, whereat the pressure in the outlet channel between the nozzle contact and the valve is lowered to the atmospheric pressure before the breaking gap is opened. Advantageously a cooling grid is arranged in the outlet channel of the leading through in- 2,969,446 Patented Jan. 24, 1961 ice sulator between the stationary nozzle contact and the blast valve. Gases heated by the arc are cooled before they reach the blast valve. Thus the volume of the gases is decreased and considerable quantities of gas per time unit can stream out through a certain valve opening. Besides it is gained that the tightening surfaces of the blast valve are to a smaller degree damaged by the heated gases from the breaking gap.

The accompanying drawing shows a form of the breaker according to the invention. In the drawing, 1 designates a stand carrying the compressed air container 2 of the circuit breaker, which is earthed and contains the operating valves and auxiliary devices necessary for the breaker, for instance indication members. The stand 1 rests on wheels 3 so that the whole circuit breaker may be moved into a switch gear cubicle and connected in by inserting the knives 4 between fork shaped contacts 5. The circuit breaker is suitably so designed that the container 2 only comprises one breaking gap and has such a volume that it contains the air quantity necessary for one interruption. It can also be made with a small volume, but then it must be con nected to a store container arranged in close vicinity. In the upper and lower walls of the container 2 insulators 6 and 7 are arranged, which are attached to the container by aid of flanges 8 and 9.

The lower insulator carries the movable contact 10 of the breaking gap, which is rigidly joined with its operating piston 11 in the cylinder 12 arranged at the inner part of the insulator 7. The space 13 above the piston 11 communicated with the inner part of the con tainer 2, so that the pressure in the container actuates the operating piston of the contact 10 in opening direction. The piston 11 is actuated in closing direction by a spring 14 in the space below the piston. This space communicates through the channel 16 in the insulator 7, the channel 17 in the end piece 18, the insulating pipe 19 and the channel 20 in the container 2 with the space 21, which can alternatively be put into communication with the container or the open air, through the valve member 22.

The upper insulator carries the stationary contact 23 of the breaking gap, which is formed as a nozzle contact, and a blast valve 24 and operating cylinder 25. The blast valve as well as the operating cylinder are arranged at the outer part of the leading through insulator, but the blast valve may also be arranged at the inner end of the leading through insulator in close vicinity of the nozzle contact 23. Between the nozzle contact 23 and the valve 24 there is a channel 26, in which an arc contact 27 and cooling grid 28 are arranged. The valve member 29 in the blast valve 24 is rigidly joined with an operating piston 30 in the operating cylinder 25. This operating piston is actuated in the closing direction of the valve by a spring 31. The space 32 above the piston 30 communicates with the valve 35 with valve members 36 and 37, by which the space 32 can alternatively be put into communication with the open air or the space 38 communicating with the container 2.

The valve member 22 is operated by a piston 40 movable in a cylinder 39, which is actuated by a spring 41 arranged in the cylinder. The space on the left hand side of the piston communicates with the open air while the space on the right hand side of the piston communicates with the operating cylinder 42 through the pipe 46. The valve members 36 and 37 are operated by an operating piston 43 which is actuated by a spring 44. The spaces on both sides of the piston communicate permanently with each other through an opening 45 in the piston 43. The space on the right hand side of the piston communicates through the pipe 49 with the valve 48, the

valve members 50 and 51 of which, which are joined with each other, can alternatively put the right hand space of the operating cylinder 42 in communication with the open air or with a space 52, which is in communication with the compressed air container 2. 53 is a spring actuating the valve members with a force actingin downward direction. The valve members can be lifted to an upper position by aid of a spring 54 actuating the piston 56 joined with the rod 55 in the operating cylinder 57. The piston 56 can be retained in its lower position by a holding magnet 58 with a release coil 59. The space below the piston 56 is permanently in communication with the open air. The space above the piston 56 communicates with a valve 60 with two valve members 61 and 62, which are joined with each other and can be lifted to an upper position by aid of a lifting magnet 63. The spring 64 actuates the valve members towards their lower position. The compressed air container 2 is supplied with compressed air through the pipe line 65 from a compressed air source, not shown on the drawing.

The circuit breaker works in the following way. When the breaking gap is closed and shall be opened, current is supplied to the release coil 59 in the holding magnet 58. Under the influence of the spring 54 the operating piston 56 and the rod 55 are displaced upwards and actuate the position of the valve members 50 and 51. The space on the right hand side of the operating piston 43, which at the lower position of the valve members 50 and 51 was in communication with the open air, is then instead put into communication with the container 2, over the space 52. The piston 43 and valve members 36 and. 37 are then moved to the left, so that the space 32 above the operating piston 30, which space in closed position of the breaker is in communication with the open air, instead is put into communication with the container 2 through the space 38. The piston 30 then displaces the valve member 29 in the blast valve to its open position, so that the air in the channel 26 can freely stream out. When the piston 43 has passed the connection of the pipe 46 with the operating cylinder 42, the space on the right hand side of the piston 40 in the operating cylinder 39 is put into communication with the container 2, so that the piston 40 can be displaced to the left by influence of the pressure in the container. The valve member 22 closes then the communication between the space 21 and the container but opens simultaneously a communication to the open air. The: space under the piston 11 in the cylinder 12 is. then evacuated so that the piston is moved downwards, by the influence of the pressure in the container, and the breaking gap is opened. Due to the fact that the blast valveis opened before the breaking gap is opened, the pressure in the channel 26 has been lowered to the atmospheric pressure when the pin contact leaves the nozzle contact 23. By this a great speed of flow through the nozzle contact and full extinguishing effect are reached immediately after the contacts have been separated. Through the channel 45 in the piston 43 air flows into the space on the left hand side of the piston. The blast valve is then kept open until. the pressure in the space on the left hand side of the piston has increased to such a value that the spring 44 is able to displace the piston 43 and valve members 36 and 37 to the right, so that the space 32 in the operating cylinder 25 again is put into-communication with the open air. The spring 31 will-then move back the piston 30 and the valve member 29 to their upper position so that the blast valve is closed. The breaking gap is closed thereby that the operating coil of the lifting magnet 63 during a short time is supplied with current. The valve members 61 and 62 are then lifted in such a way that the communication between the space above the piston 56 and the open air is interrupted and instead a communication between this space and the container 2 is effected. The piston 56, which at the same time may constitute the armature of the holding. magnet, is then removed to its original position, and the valve members 50 and 51 in the valve 48 are moved downwards by the spring 53. The space in the cylinder 42 on the right hand side of the piston 43 is then again put into communication with the open air. The pipe 46 and the space in the cylinder 39 on the right hand side of the piston 40 are the-n also evacuated through the opening 45. The spring 41 moves then the piston 40 and the valve member 22 so that there is again a communication between the container 2 and the space in the cylinder 12 under the operating piston 11. The spring 14 moves then the piston with the pin contact 10' upwards and the breaking gap is closed.

I claim as my invention:

1. An air blast circuit breaker comprising a metal container permanently filled with compressed air, a movable breaking contact and a stationary breaking contact both arranged within said container, two leading through insulators inserted in the walls of the container and each carrying one of said contacts, a cylinder with an operating piston connected with said movable contact and carried by the insulator which carries the said movable contact, a blast valve carried by the insulator that carries the said stationary contact, an outlet channel for the compressed air in the latter insulator, and means whereby after the circuit is broken the said contacts are held in their open position so that a breaking gap of compressed air is located between them.

2. Air blast circuit breaker according to claim 1, in which the operating piston of the movable contact is actuated in opening direction by the pressure in the container.

3. Air blast circuit breaker according to claim 1, in which the blast valve is arranged in a valve housing located at the outer part of the one leading through insulator.

4. Air blast circuit breaker according to claim 3, in which the blast valve is opened earlier than the breaking gap, so that the pressure in the outlet channel be tween the nozzle contact and the valve is lowered before the breaking gap is opened.

5. Air blast circuit breaker according to claim 3, in which a cooling grid is arranged between the stationary nozzle contact and the blast valve in the outlet channel of the leading through insulator.

References Cited in the tile of this patent UNITED STATES PATENTS 2,153,400 Trencham Apr. 4, 1939 2,459,600 Strom Jan. 18, 1949 2,507,210 Ludwig et al. May 9, 1950 2,665,351 Forwald a- Jan. 5, a

FOREIGN PATENTS 997,193 France Sept. 12, 1951 

